The present invention relates to a vinyl chloride resin excellent in adhesive strength and a process for the preparation of such resin. More particularly, the invention relates to a vinyl chloride resin for a safety glass which can give safety glass excellent in the resistance to penetration and impact and also to a process for the preparation of this resin.
As is well known, a plasticized polyvinyl butyral film has been used as an interlayer for a safety glass. However, this plasticized polyvinyl butyral film has a problem in that the surface of the film is highly self-adhesive to cause blocking in the winding step after the molding of the film. Therefore, it has been necessary in order to inhibit the blocking that the film is embossed and sprayed with an anti-blocking agent such as sodium hydrogen carbonate.
Meanwhile, vinyl chloride-glycidyl methacrylate copolymer film containing about 40 % by weight of a plasticizer has been known as a film which hardly causes blocking. Further, Japanese Patent Application Kokai Publication No. 55-162451 has proposed an interlayer made of a composition which comprises a copolymer comprising vinyl chloride, glycidyl methacrylate and at least one monomer selected from among ethylenically unsaturated hydrocarbons, vinyl esters of fatty acids, acrylates and vinyl ethers, and a plasticizer.
The adhesive strength of each of these vinyl chloride copolymers to glass can be improved by changing the glycidyl methacrylate content thereof. However, an increase in the glycidyl methacrylate content brings about a lowering in the penetration resistance of the resulting safety glass, so that it is difficult to obtain a safety glass excellent in both adhesive strength and penetration resistance. Further, such an increase lowers the yield in the polymerization or gives a copolymer which is lowered in heat stability to cause discoloration. Moreover, it tends to occur during the preparation of the copolymer resin that scales become attached on the wall surface of the polymerization reactor and/or that the plastisol undergoes a change (an increase in the viscosity) with the lapse of time.